This disclosure relates to the removal of heat from a gearbox.

In many industrial applications, some engine components (e.g., a gearbox or transmission) generate heat during operation. Lubricant applied within the component facilitates heat transfer and prevents damage due to the generation of excessive heat. Managing the heat generated by a component can be an important safety consideration. European patent application EP2,738,426 A1 describes a cooling system configured to promote heat transfer in a gearbox. The system can include a container for housing a gas, the gas having a sufficient percentage of helium so that once the gas is introduced into the gearbox, the helium increases heat transfer from the heat generating components of the gearbox. The generic document US 5,344,101 discloses a safeguard system for a helicopter gearbox in case of lubricating oil loss, in which an additional air circulation cooling system is activated under the effect of a control device at a preset value of a parameter significant for lubricating oil loss to provide circulation of coolant between an inlet and outlet of the gearbox.

This disclosure describes technologies relating to removing heat from a transmission with compressed gas. The invention concerns a cooling system and a method comprising the features of claims 1 and 7. Embodiments of the invention are provided by the appended dependent claims.

The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

• FIG. 1 is a schematic diagram showing an example cooling system.
• FIG. 2 is a flowchart showing an example process for cooling a component.
• FIG. 3 is a cross-sectional view of an example gearbox including parts of an example cooling system.
• FIG. 4A is a schematic diagram showing an example controller module.
• FIG. 4B is a schematic diagram showing an example of a controller implemented as a computing system.
• FIG. 5 is a schematic diagram showing an example of a rotorcraft.
• FIG. 6 is a schematic diagram showing an example of a tiltrotor aircraft.

Like reference numbers and designations in the various drawings indicate like elements.

This disclosure relates to an aircraft gaseous cooling system. Some industrial applications use a variety of lubrication systems to provide wear protection and heat transfer within components such as a gearbox or transmission. Under normal operating conditions, lubrication systems provide proper lubrication and heat removal. However, lubrication systems can fail, resulting in excessive wear and failure of components. Backup cooling systems can provide lubrication if the primary lubrication system fails, for example, for an aircraft (such as a rotorcraft) to maintain manageable flight operations for a duration if the primary lubrication system fails. In some cases, backup cooling systems, such as increased lubrication reserves or a secondary lubrication system, can be used. However, these can add weight and can fail to provide adequate cooling.

This disclosure describes an active cooling system to cool a mechanical component such as a gearbox, transmission, or other component. The cooling system uses a gas source (e.g., a compressor) to continuously supply compressed gas to the component. The compressed gas floods the component and convects heat generated within the component. In some implementations, the generated heat can be transferred from the compressed gas to the component housing where the heat is dissipated, and in some implementations the heat can be transferred from the compressed gas to the atmosphere. A compressed gas supplied at a higher pressure to the component can have improved convective heat transfer characteristics over a gas at a lower pressure (e.g. atmospheric pressure) due to the increased density of the compressed gas. Also, compressing the gas allows a relatively rapid transfer of the gas from the gas source to the component compared to uncompressed gas. A continuous supply ensures that a larger volume of gas is available for cooling over time. As such, a continuous supply of gas can cool the component for a longer duration than a single-use supply of gas. In some implementations, the continuous supply of compressed gas can provide cool gas multiple discrete times.

The disclosed cooling system can be used during normal operation or used as a backup cooling system in response to a failure of a lubricant system. For example, the cooling system can be in a passive state until a primary lubrication system failure occurs and then the cooling system can operate to cool to the component. In some aircraft implementations, the cooling system can provide cooling for the minimum flight time when the primary lubrication system fails. In some implementations, the cooling system can enhance or extend the minimum flight time. The cooling system described can have less weight or volume than other cooling systems such as backup lubrication systems. In some implementations, the cooling system can be added to an existing component or system, e.g., as an add-on kit.

FIG. 1 illustrates a schematic diagram of an example cooling system 100. The cooling system 100 is connected to a component 102 to be cooled. The component 102 can be a component such as an engine, a gearbox, a transmission, or another component. For example, the component 102 can be a gearbox in a rotorcraft. The component 102 is connected to a gas source 104 via a gas line 106. The gas source 104 is configured to supply compressed gas to the interior of component 102 through the gas line 106. For example, the gas source 104 can be a compressor that pressurizes the gas. The gas source 104 can be powered by an engine such as an electrical or hydraulic engine, directly shafted and or clutched to the 102 component, or by another technique.

The compressed gas supplied by the gas source 104 is a gas with a favorable heat transfer coefficient to transfer heat from the component 102. For example, the compressed gas can be a gas such as helium, air, argon, polymer gas, hydrocarbon gas, or another gas. The compressed gas can also be a mixture of gases, for example, a mixture of 80% helium and 20% argon. The compressed gas can also be atmospheric air pressurized by the gas source 104. The compressed gas can be supplied to the gas source 104 from a separate gas container. For example, containers containing types of gases can be attached to the gas source 104 to generate compressed gases of a type other than air.

An inlet valve 112 can be positioned in the gas line 106 to permit or deny flow of the compressed gas from the gas source 104 to the component 102. The inlet valve 112 can be positioned at the component 102, at the gas source 104, or at any suitable location along the gas line 106.

The cooling system 100 also includes a detection sensor 114 that is coupled to the component 102. The detection sensor 114 can detect if the lubrication system in the component 102 has failed. For example, the detection sensor 114 can include a sensor such as a pressure sensor, temperature sensor, lubrication sensor (e.g., oil pressure sensor), a pressure sensor, combinations of them, or another sensor. In some implementations, the detection sensor 114 includes more than one sensor or more than one type of sensor.

The cooling system 100 also includes a vent valve 108 that is coupled to the component 102. The vent valve 108 can open to vent the compressed gas within the component 102 to the atmosphere. In this manner, the heat transferred to the compressed gas can be then transferred to the atmosphere. If the pressure of the gas within the component 102 is too high, damage to seals and other sub-components can occur. In such a case, the vent valve 108 can open to reduce the pressure within the component 102.

The cooling system 100 also includes a controller 110. The controller 110 can be communicatively connected to the gas source 104, the inlet valve 112, the vent valve 108, and/or the detection sensor 114. In some implementations, the controller 110 can control vent valve 108, inlet valve 112, and gas source 104 to selectively control the introduction of the pressurized gas into the component 102 and the release to atmosphere of gas from the component 102. In this manner, the controller 110 can control the rate at which gas is transferred from the gas source 104 to the component 102 to control the rate of cooling of the component 102. The controller 110 can also control the rate of gas transfer to increase the supply of compressed gas to compensate for gas lost to leaky component 102 seals. The controller 110 can provide inputs to the cooling system 100 components so that a desired pressure of the gas is reached and maintained within the component 102.

The controller 110 is configured to send inputs to the connected components. For example, the controller 110 can send an input to start or stop the gas source 104 or open or close a valve 108, 112. The controller 110 is also configured to receive inputs from connected components. For example, the controller 110 can receive a signal from detection sensor 114. In another example, in response to a high pressure detected in the component 102, the controller 110 can provide an input to the gas source 104 to stop supplying compressed gas to the component 102, or the controller can provide an input to the inlet valve 112 to close the inlet valve 112 to stop the supply of compressed gas to the component 102. In a further example, in response to a high temperature determined by the detection sensor 114, the controller 110 can provide an input to the vent valve 108 to vent the heated gas and provide an input to the inlet valve 112 or gas source 104 to supply fresh, cooler compressed gas. Any of these methods may be used alone or in combination to control the pressure or flow of compressed gas in the cooling system 100.

In another example, the controller 110 can send an input to vent valve 108 to vent the compressed gas from the component 102 to atmosphere. The detection sensor 114 can monitor a pressure in the component 102 in response to the compressed gas being flowed to the component 102 from the gas source 104. For example, the controller 110 can delay the closure of vent valve 108 until the gas within the component reaches a certain pressure. If the pressure in the component 102 is greater than a threshold pressure, the controller 110 can provide an input to the vent valve 108 to vent the compressed gas. In some implementations, the controller 110 is included as part of another system, such as a computer system or other data processing apparatus. For example, the controller 110 can be incorporated as part of the avionics system on an aircraft.

In some implementations, the cooling system 100 includes one or more mechanical interlocks (not shown) to control the gas source 104, inlet valve 112, and vent valve 108. In some implementations, one or more pressure-activated switches or valves coupled to the component 102 control the gas supply into the component 102 or gas venting out of the component 102. For example, a pressure switch coupled to the vent valve 108 can open vent valve 108 when the pressure in the component 102 surpasses a threshold pressure determined by the switch. Other types of switches or valves can be used that monitor temperature, lubrication quantity, or other characteristics. In this manner, in some implementations, parts of the cooling system 100 function without electrical operation or without a controller 110.

FIG. 2 is a flowchart of an example aircraft gaseous cooling process 200. The example aircraft gaseous cooling process 200 can be implemented by example cooling system 100, for example. FIG. 3 shows a cross-sectional view of an example gearbox 300 that is cooled by cooling process 200. The gearbox 300 can be coupled to another component or system such as an engine, aircraft, automobile, or other system as described below. The gearbox 300 includes a housing 302 that encloses internal heat-generating sub-components (e.g. gears, bearings). The housing 302 defines an interior volume 308 of the gearbox 300. The example gearbox 300 includes an example rotary shaft 304 that is coupled to and rotated by internal sub-components. The rotary shaft 304 can be coupled to a system such as a rotor, axle, gearing, or other mechanical system. In some implementations, the rotary shaft 304 is coupled to the gas source 104 (e.g., via an accessory shaft) and the gas source 104 receives power from the rotary shaft 304 to generate the compressed gas 310.

The gas line 106 conducts compressed gas 310 from the gas source 104 to the interior volume 308. The compressed gas 310 in the interior volume 308 convects heat from the heat-generating sub-components and transfers the heat to the housing 302. The heat can then be transferred from the housing 302 to the atmosphere, for instance. The gearbox 300 can also include a vent valve 108 that allows the compressed gas 310 to vent to the atmosphere, transferring the heat from the compressed gas 310 to the atmosphere. In some implementations, the compressed gas 310 is vented into the atmosphere through gearbox 300 seals. The exact locations of gas line 106 and vent valve 108 are implementation specific. Furthermore, the gas line 106 and vent valve 108 can be coupled to gearbox 300 at any practical location.

At 210, the cooling system 100 determines that the lubrication system has failed in gearbox 300. The lubrication system failure can be determined by a detection sensor 114 positioned within the interior of gearbox 300. More than one detection sensor 114 can be positioned within or on the exterior of gearbox 300, and each detection sensor 114 can be positioned at any practical location. In one implementation, the detection sensor 114 includes a pressure sensor (not shown) within gearbox 300 that detects the lubrication failure in response to a pressure in gearbox 300 being greater than a threshold pressure. For example, if the lubrication system has failed, the heat generated in gearbox 300 can increase pressure of the gas within gearbox 300, and the pressure sensor can detect this increased pressure. The pressure sensor may be a pressure transducer, strain gauge, Bourdon tube with deflection gauge, or other active or passive sensor.

Many lubrication systems use pressurized lubricant, and a drop in lubricant pressure can be indicative of lubrication system failure. As such, the detection sensor 114 can also include a pressure sensor (not shown) that detects a lubrication failure in response to a pressure of the lubricant in the lubrication system or gearbox 300 being less than a threshold pressure. In some implementations, the detection sensor 114 detects the quantity of lubrication present in the lubrication system or in gearbox 300, where a low quantity of lubrication is indicative of lubrication system failure. As such, the detection sensor 114 can include a lubrication quantity sensor (not shown) that detects the lubrication failure in response to a lubricant quantity in gearbox 300 being less than a threshold lubricant quantity.

Once a lubrication system fails, one or more sub-components within gearbox 300 can generate excess heat. As such, the detection sensor 114 can include a temperature sensor (not shown) to detect a lubrication failure in response to a temperature in gearbox 300 being greater than a threshold temperature. For example, a temperature sensor can detect the temperature of one or more sub-components (e.g. gears, bearings, or other sub-components) within gearbox 300. A temperature sensor can also detect the temperature of gas within gearbox 300. In other implementations, a temperature sensor detects the temperature of the housing 302 or an interior or exterior surface of gearbox 300. The detection sensor 114 can include more than one temperature sensor.

At 220, the cooling system 100 continuously supplies compressed gas to gearbox 300 in response to determining the lubrication system has failed. In some implementations, the detection sensor 114 provides notification to the controller 110 when a lubrication failure is determined. The controller 110 then provides an input to the gas source 104 or other cooling system 100 components in response to the lubrication failure. For example, the controller 110 can start the gas source 104 to supply the compressed gas to gearbox 300. In some implementations, the controller 110 sends an input to an inlet valve 112. For example, if the gas source 104 has generated compressed air, the input can open the inlet valve 112 to release the accumulated compressed air into gearbox 300.

FIG. 4A shows a first implementation of the controller 110. The example controller module 400 shown in FIG. 4A can be implemented as processing circuitry 402. The processing circuitry 402 may perform methods of various aspects of the subject matter described in this disclosure, such as one or more of the operations related to FIGS. 1-3. The processing circuitry 402 can include memory for storing data or instructions, including instructions embodying aspects of the subject matter described in this disclosure. The processing circuitry 402 is configured to communicate with other modules, systems, or components. For example, the processing circuitry 402 can send inputs to cooling system 100 components such as gas source 104 and valves 108, 112.

FIG. 4B shows a second implementation of the controller 110 as a computer system 450. The system 450 includes an interface 404 and a data processing apparatus 452 (e.g., one or more processors) to execute computer instructions stored on a computer-readable medium 454 to perform operations of the cooling system 100.

FIG. 5 is a schematic diagram of an example rotorcraft 501. Rotorcraft 501 has a rotor system 503 with multiple rotor blades 505. Rotorcraft 501 can further include a fuselage 507, anti-torque system 509, and an empennage 511. The rotorcraft 501 can also include a cooling system, such as example cooling system 100. The cooling system 100 can be implemented in one or more gearbox or transmission assemblies of the rotorcraft 501, as described previously.

FIG. 6 is a schematic diagram of an example tiltrotor aircraft 601. Aircraft 601 includes a fuselage 607 with attached wings 605 and landing gear 209. Nacelles 603 are carried at the outboard ends of wings 605 and are rotatable between the helicopter-mode position shown and a forward-facing airplane-mode position (not shown). Nacelles 603 carry engines and transmissions for powering rotor systems 611 in rotation. An engine may be an internal combustion engine, an electrical power source and associated motor, or any other suitable technique for powering rotor system 611. The tiltrotor aircraft 601 can include a cooling system such as example cooling system 100 implemented in one or more gearbox or transmission assemblies of the tiltrotor aircraft 601

The cooling system described in this disclosure can be implemented in a rotorcraft such as shown in FIG. 5 or in a tiltrotor aircraft such as shown in FIG. 6. Indeed, the cooling system can be implemented in any aircraft having a drivetrain component. Furthermore, the cooling system can be used in applications where a component may require heat rejection, including systems with a gearbox or transmission. For example, the cooling system can be implemented in automotive systems (e.g. automobiles, ATVs, motorcycles, or other automotive systems), fixed-wing aircraft, submersible systems, marine systems (e.g. personal watercraft, boats, or other marine systems), agricultural systems (e.g. tractors or other agricultural systems), power equipment (e.g. generators, lawn mowers, or other power equipment), construction equipment (e.g. industrial vehicles, heavy machinery, or other equipment) or other systems.